A cAMP-biosensor-based assay for measuring plasma arginine-vasopressin levels

Arginine-vasopressin (AVP), a cyclic peptide hormone composed of nine amino acids, regulates water reabsorption by increasing intracellular cyclic adenosine monophosphate (cAMP) concentrations via the vasopressin V2 receptor (V2R). Plasma AVP is a valuable biomarker for the diagnosis of central diabetes insipidus (CDI) and is commonly measured using radioimmunoassay (RIA). However, RIA has several drawbacks, including a long hands-on time, complex procedures, and handling of radioisotopes with special equipment and facilities. In this study, we developed a bioassay to measure plasma AVP levels using HEK293 cells expressing an engineered V2R and a cAMP biosensor. To achieve high sensitivity, we screened V2R orthologs from 11 various mammalian species and found that the platypus V2R (pV2R) responded to AVP with approximately six-fold higher sensitivity than that observed by the human V2R. Furthermore, to reduce cross-reactivity with desmopressin (DDAVP), a V2R agonist used for CDI treatment, we introduced a previously described point mutation into pV2R, yielding an approximately 20-fold reduction of responsiveness to DDAVP while maintaining responsiveness to AVP. Finally, a comparison of plasma samples from 12 healthy individuals demonstrated a strong correlation (Pearson's correlation value: 0.90) between our bioassay and RIA. Overall, our assay offers a more rapid and convenient method for quantifying plasma AVP concentrations than existing techniques.

Role of Membrane Lipid Rafts in MRP4 (ABCC4) Dependent Regulation of the cAMP Pathway in Blood Platelets

BACKGROUND

Platelet cytosolic cyclic adenosine monophosphate (cAMP) levels are balanced by synthesis, degradation, and efflux. Efflux can occur via multidrug resistant protein-4 (MRP4; ABCC4) present on dense granule and/or plasma membranes. As lipid rafts have been shown to interfere on cAMP homeostasis, we evaluated the relationships between the distribution and activity of MRP4 in lipid rafts and cAMP efflux.

METHODS

Platelet activation and cAMP homeostasis were analyzed in human and wild-type or MRP4-deleted mouse platelets in the presence of methyl-β-cyclodextrin (MßCD) to disrupt lipid rafts, and of activators of the cAMP signalling pathways. Human platelet MRP4 and effector proteins of the cAMP pathway were analyzed by immunoblots in lipid rafts isolated by differential centrifugation.

RESULTS

MßCD dose dependently inhibited human and mouse platelet aggregation without affecting per se cAMP levels. An additive inhibitory effect existed between the adenylate cyclase (AC) activator forskolin and MßCD that was accompanied by an overincrease of cAMP, and which was significantly enhanced upon MRP4 deletion. Finally, an efflux of cAMP out of resting platelets incubated with prostaglandin E1 (PGE1) was observed that was partly dependent on MRP4. Lipid rafts contained a small fraction (≈15%) of MRP4 and most of the inhibitory G-protein Gi, whereas Gs protein, AC3, and phosphodiesterases PDE2 and PDE3A were all present as only trace amounts.

CONCLUSION

Our results are in favour of part of MRP4 present at the platelet surface, including in lipid rafts. Lipid raft integrity is necessary for cAMP signalling regulation, although MRP4 and most players of cAMP homeostasis are essentially located outside rafts.

Transcriptome analysis of the effect of diosgenin on autoimmune thyroiditis in a rat model

In a mouse model of Graves' disease (GD), diosgenin has been shown to have a therapeutic effect on GD by alleviating goitre. However, research on the effect of diosgenin on autoimmune thyroiditis (AIT) is lacking. In this study, transcriptomics was used to comprehensively analyse the protective effect of diosgenin against AIT in rats and the possible mechanism. The results showed that in the diosgenin-intervention group, compared to the model group, the expression of serum triiodothyronine, thyroxine, free triiodothyronine, and free thyroxine was decreased and that of thyroid-stimulating hormone was increased; these changes were accompanied by the downregulation of thyroglobulin, TSH receptor antibody and thyroid peroxidase expression in serum. Furthermore, transcriptome detection, RT-qPCR and immunohistochemistry verification revealed that in thyroid tissue, the relative mRNA and protein expression of cyclic adenosine 3',5'-monophosphate (cAMP), protein kinase A (PKA) and cAMP response element-binding protein (Creb) were increased and the mRNA expression of S100 calcium-binding protein A9 (S100A9) was decreased in the diosgenin groups. In summary, diosgenin alleviates the development of AIT, possibly via the activation of the cAMP/PKA/Creb pathway and downregulation of S100A9 gene expression.

Analgesic action of Rubimaillin in vitro and in vivo

Pain, a common symptom in clinics, is a serious impediment to quality of life. The analgesic drugs presently in use have poor efficacy, and are associated with undesirable side effects. Rubimaillin (Rub) is a naphthoquinone compound extracted from Chinese herbal medicine, and it has various biological activities. In this study, the analgesic effect of Rub, and its mechanism of action were investigated using glacial acetic acid-induced mice writhing model and a mice model of neurogenic and inflammatory bipolar pain. Analgesic effects were measured in different experimental groups. In vitro, RAW 264.7 cells were used to investigate the release of nitric oxide (NO), iNOS and COX-2 protein in RAW 264.7 cells stimulated with lipopolysaccharide (LPS). The results revealed that Rub reduced the number of acetic acid-induced writhing in mice, inhibited formalin-induced biphasic pain response, and suppressed the production of NO in RAW 264.7 cells. The mechanisms involved in the analgesic and anti-inflammatory effects of rub may be related to the inhibition of cyclooxygenase-2 (COX-2), endogenous inflammatory mediators, and reduction in the content of pain-induced mediators.

Biomarker-specific differences between transpulmonary and peripheral arterial-venous blood sampling in patients with pulmonary hypertension

Purpose: Transpulmonary biomarkers may provide insight into pulmonary hypertension (PH) pathophysiology, but require cardiac catheterization. We investigated whether the peripheral arterial-venous ratio (PR) could substitute for the transpulmonary ratio (TPR).Materials and methods: Blood from the pulmonary artery (PA), pulmonary arterial wedge (PAW), peripheral venous, and peripheral arterial positions was analysed for ET-1, NT-pro-BNP and cAMP levels in subjects with no PH (n = 18) and PH due to left heart disease (PH-LHD), which included combined pre- and post-capillary PH (Cpc-PH; n = 7) and isolated post-capillary PH (Ipc-PH; n = 9). Bland-Altman comparisons were made between peripheral venous and PA samples and between peripheral arterial and PAW samples. TPR was defined as [PAW]/[PA].Results: For ET-1, Bland-Altman analysis indicated negative bias (-24%) in peripheral arterial compared to PAW concentration and positive bias (23%) in peripheral venous compared to PA concentration. There was <10% absolute bias for NT-pro-BNP and cAMP. For ET-1, there was no difference in PR between Cpc-PH and Ipc-PH (0.87 ± 0.4 vs. 0.94 ± 0.6, p = 0.8), whereas there was a difference in TPR (2.2 ± 1.1 vs. 1.1 ± 0.2, p < 0.05).Conclusions: In PH-LHD, peripheral samples may be inadequate surrogates for transpulmonary samples, particularly when measuring mediators with prominent pulmonary secretion or clearance, such as ET-1.

Effect of Different Doses of Acetylsalicylic Acid on the Antithrombotic Activity of Clopidogrel in a Mouse Arterial Thrombosis Model

Objective- Dual-antiplatelet therapy with acetylsalicylic acid and a P2Y₁₂ antagonist, such as clopidogrel, is the standard of care for acute coronary syndromes. However, the drugs have divergent effects on the formation of cAMP, an inhibitory second messenger. Thus, by inhibiting the synthesis of prostacyclin, acetylsalicylic acid reduces cAMP formation, whereas clopidogrel potentiates it. Therefore, with higher doses of acetylsalicylic acid, the potentiation of cAMP production by clopidogrel may be attenuated, which could limit the antithrombotic potential of the drug combination. The purpose of this study was to examine this possibility in vivo. Approach and Results- Mice were given oral acetylsalicylic acid at varying doses, oral clopidogrel (5 mg/kg body weight), or both. At doses of 0.15 and 0.6 mg/kg, acetylsalicylic acid inhibited arachidonic acid-induced platelet aggregation, but only 0.6 mg/kg acetylsalicylic acid, or higher, decreased the plasma levels of 6-keto-prostaglandin-F_1α, the stable metabolite of prostacyclin. When given with clopidogrel, laser injury-induced arterial thrombi were significantly larger with the 0.6 mg/kg dose of acetylsalicylic acid than with the 0.15 mg/kg dose. Thrombi in mice treated with clopidogrel and the 0.15 mg/kg dose of acetylsalicylic acid were smaller than in mice treated with clopidogrel alone, suggesting that acetylsalicylic acid can add to the antithrombotic effect of clopidogrel but that higher doses of acetylsalicylic acid blunt the antithrombotic effect of clopidogrel. Conclusions- These findings support the use of lower, prostacyclin-preserving, doses of acetylsalicylic acid in conjunction with clopidogrel.

The formyl peptide fMLF primes platelet activation and augments thrombus formation

Essentials The role of formyl peptide receptor 1 (FPR1) and its ligand, fMLF, in the regulation of platelet function, hemostasis, and thrombosis is largely unknown. Fpr1-deficient mice and selective inhibitors for FPR1 were used to investigate the function of fMLF and FPR1 in platelets. N-formyl-methionyl-leucyl-phenylalanine primes platelet activation and augments thrombus formation, mainly through FPR1 in platelets. Formyl peptide receptor 1 plays a pivotal role in the regulation of platelet function.

BACKGROUND

Formyl peptide receptors (FPRs) play pivotal roles in the regulation of innate immunity and host defense. The FPRs include three family members: FPR1, FPR2/ALX, and FPR3. The activation of FPR1 by its high-affinity ligand, N-formyl-methionyl-leucyl-phenylalanine (fMLF) (a bacterial chemoattractant peptide), triggers intracellular signaling in immune cells such as neutrophils and exacerbates inflammatory responses to accelerate the clearance of microbial infection. Notably, fMLF has been demonstrated to induce intracellular calcium mobilization and chemotaxis in platelets that are known to play significant roles in the regulation of innate immunity and inflammatory responses. Despite a plethora of research focused on the roles of FPR1 and its ligands such as fMLF on the modulation of immune responses, their impact on the regulation of hemostasis and thrombosis remains unexplored.

OBJECTIVE

To determine the effects of fMLF on the modulation of platelet reactivity, hemostasis, and thrombus formation.

METHODS

Selective inhibitors for FPR1 and Fpr1-deficient mice were used to determine the effects of fMLF and FPR1 on platelets using various platelet functional assays.

RESULTS

N-formyl-methionyl-leucyl-phenylalanine primes platelet activation through inducing distinctive functions and enhances thrombus formation under arterial flow conditions. Moreover, FPR1 regulates normal platelet function as its deficiency in mouse or blockade in human platelets using a pharmacological inhibitor resulted in diminished agonist-induced platelet activation.

CONCLUSION

Since FPR1 plays critical roles in numerous disease conditions, its influence on the modulation of platelet activation and thrombus formation may provide insights into the mechanisms that control platelet-mediated complications under diverse pathological settings.

Global expression profiling and pathway analysis in two different population groups in relation to high altitude

High altitude (HA) is associated with number of stresses. Response of these stresses may vary in different populations depending upon altitude, duration of residency, ancestry, geographical variation, lifestyle, and ethnicities. For understanding population variability in transcriptome, array-based global gene expression profiling was performed on extracted RNA of male volunteers of two different lowland population groups, i.e., Indians and Kyrgyz, at baseline and day 7 of HA exposure (3200 m). A total of 97 genes were differentially expressed at basal in Kyrgyz as compared to Indians (82 downregulated and 15 upregulated), and 196 were differentially expressed on day 7 of HA (118 downregulated and 78 upregulated). Ingenuity Pathway Analysis and gene ontology highlighted eIF2 signaling with most significant negative activation z score at basal in Kyrgyz compared to Indians with downregulation of various L- and S-ribosomal proteins indicating marked translational repression. On day 7, cAMP-mediated signaling is most enriched with positive activation z score in Kyrgyz compared to Indians. Plasma cAMP levels were higher in Kyrgyz on day 7 compared to Indians. Extracellular adenosine levels were elevated in both the groups upon HA, but higher in Kyrgyz compared to Indians. Valedictory qRT-PCR showed upregulation of ADORA2B and CD73 along with downregulation of ENTs in Kyrgyz compared to Indians indicating elevated levels of extracellular nucleotides mainly adenosine and activation of extracellular cAMP-adenosine pathway which as per literature triggers endogenous protective mechanisms under stress conditions like hypoxia. Thus, transcriptome changes at HA are population-specific, and it may be necessary to take care while interposing similar results in different populations.

Total flavonoid extract of Epimedium herb increases the peak bone mass of young rats involving enhanced activation of the AC10/cAMP/PKA/CREB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Epimedium sagittatum brevicornum Maxim. is an important traditional Chinese herb that has long been used to promote bone fracture healing and treat osteoporosis.

AIM OF THE STUDY

Achieving peak bone mass by adolescence has now been accepted to be fundamental for preventing osteoporosis in adulthood life. This study investigated the possibility of increasing peak bone mass in young rats using the total flavonoid extract of Epimedium herb (TFE).

MATERIALS AND METHODS

TFE was intragastrically administered to one-month-old Wistar rats at a low (100 mg/kg), middle (200 mg/kg) or high dose (400 mg/kg). Whole body bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry every two weeks. When BMD of any one of TFE groups was found to be significantly higher than that of the control, all rats were sacrificed, serum samples were collected for bone turnover biochemical assays, and femurs, tibiae and vertebrae were isolated and used in BMD, mechanical, micro-structural, histomorphometric and mechanistic studies.

RESULTS

Administration of TFE at middle and high doses for two months significantly increased the whole body, femoral and vertebral BMDs, and improved the bone mechanical and micro-architectural properties. The serum turnover biochemical results and the enhanced expression levels of bone-formation regulatory genes (Runx-2, OSX, and BMP-2) demonstrated that TFE administration increased bone formation but had no effect on bone resorption. The increased phosphorylation levels in femurs of PKA and CREB and expression of AC10 (the only soluble form of adenylyl cyclase) and the increased serum cAMP level after 4 h of TFE administration indicated that TFE promoted bone formation by activating the AC10/cAMP/PKA/CREB pathway in vivo.

CONCLUSIONS

Oral administration of TFE at 200 mg/kg for two months can increase the peak bone mass of growing rats, suggesting the possibility of using total flavonoid extract of Epimedium herb to increase the peak bone mass in adolescence which is important for preventing osteoporosis in adult life.

Exenatide induces an increase in vasodilatory and a decrease in vasoconstrictive mediators

In view of the known vasodilatory effects of glucagon-like peptide-1 and exenatide, we investigated the effects of exenatide on vasoactive factors. We analysed blood samples and mononuclear cells (MNCs) from a previous study, collected after a single dose and 12 weeks of exenatide or placebo treatment in a series of 24 patients with type 2 diabetes mellitus. After exenatide treatment, plasma concentrations of atrial natriuretic peptide, cyclic guanyl monophosphate (cGMP) and cyclic adenyl monophosphate increased significantly at 12 weeks. Plasma cGMP and adenylate cyclase expression in MNCs increased significantly after a single dose. Angiotensinogen concentration fell significantly 2 hours after a single dose and at 12 weeks, while renin and angiotensin II levels fell significantly only after a single dose and not after 12 weeks of treatment. Exenatide also suppressed the plasma concentration of transforming growth factor-β and the expression of P311 in MNCs at 12 weeks. Thus, exenatide induces an increase in a series of vasodilators, while suppressing the renin-angiotensin system. These changes may contribute to the overall vasodilatory effect of exenatide.

Fgf23 and parathyroid hormone signaling interact in kidney and bone

Fibroblast growth factor-23 (FGF23) is a bone-derived hormone, suppressing renal phosphate reabsorption and vitamin D hormone synthesis in proximal tubules, and stimulating calcium reabsorption in distal tubules of the kidney. Here, we analyzed the long term sequelae of deficient Fgf23 signaling on bone and mineral metabolism in 9-month-old mice lacking both Fgf23 or Klotho and a functioning vitamin D receptor (VDR). To prevent hypocalcemia in VDR deficient mice, all mice were kept on a rescue diet enriched with calcium, phosphate, and lactose. VDR mutants were normocalcemic and normophosphatemic, and had normal tibial bone mineral density. Relative to VDR mutants, Fgf23/VDR and Klotho/VDR compound mutants were characterized by hypocalcemia, hyperphosphatemia, and very high serum parathyroid hormone (PTH). Despite ∼10-fold higher serum PTH levels in compound mutants, urinary excretion of phosphate and calcium as well as osteoclast numbers in bone remained unchanged relative to VDR mutants. The increase in plasma cAMP after hPTH(1-34) injection was similar in all genotypes. However, a 5-day infusion of hPTH(1-34) via osmotic minipumps resulted in reduced phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in bone and kidney of Fgf23/VDR and Klotho/VDR compound mutants, relative to VDR and WT controls. Similarly, the PTH-mediated ERK1/2 phosphorylation was reduced in primary osteoblasts isolated from Fgf23 and Klotho deficient mice, but was restored by concomitant treatment with recombinant FGF23. Collectively, our data indicate that the phosphaturic, calcium-conserving, and bone resorption-stimulating actions of PTH are blunted by Fgf23 or Klotho deficiency. Hence, FGF23 may be an important modulator of PTH signaling in bone and kidney.

Tetramethylpyrazine identified by a network pharmacology approach ameliorates methotrexate-induced oxidative organ injury

ETHNOPHARMACOLOGICAL RELEVANCE

Tetramethylpyrazine (TMP) is one of the active constituents extracted from a frequently used herb, Ligusticum wallichii Franchat (Chuan-Xiong in Chinese), in traditional Chinese medicine. TMP can exert multiple pharmacological actions such as anti-inflammatory, anti-oxidative damage, anti-platelet and neuroprotective effects, and its applications deserve further explored.

AIM OF THE STUDY

This study aimed to determine the new role of TMP identified by a network pharmacology approach to alleviate the methotrexate (MTX)-induced oxidative injury and characterize their mechanism of combinational actions.

MATERIALS AND METHODS

A network pharmacology-based screening strategy is applied for target profile prediction and pharmacological characterization of herbal compounds, which is used to guide the following in vitro and in vivo experiments. The effect of herbal compounds identified by network pharmacology approaches to reduce the toxicity of MTX was assessed by MTX-induced rat toxicity model. The potential targets of TMP in this study were evaluated using standard protocols provided by Cerep, Inc.

RESULTS

This strategy identified TMP from Ligusticum wallichii Franchat as a potent compound for ameliorating the oxidative organ injury of MTX. According to the predicted target profiles of TMP, a possible mechanism of the abrogation of MTX-induced toxicity is that TMP could upregulate cAMP by inhibiting phosphodiesterase (PDE) 10A2 activity. Another novel finding is that the competitive binding and antagonistic effects of TMP on adenosine receptor 2A and 2B appear to play important roles in the TMP-mediated reversal of MTX-induced hepatic injury.

CONCLUSION

TMP identified by a network pharmacology approach could ameliorate MTX-induced oxidative organ injury. This study provides important evidence for the preclinical evaluation of TMP and MTX as a novel combinatorial remedy.

Adrenomedullin induces pulmonary vasodilation but does not attenuate pulmonary hypertension in a sheep model of acute pulmonary embolism

AIMS

The pulmonary vasodilation induced by adrenomedullin may be beneficial in the acute pulmonary embolism (APE) setting. This study examined effects of adrenomedullin in sheep with microsphere-induced APE.

MAIN METHODS

Twenty four anesthetized, mechanically ventilated sheep were randomly assigned into 3 groups (n=8 per group): animals not subjected to any intervention (Sham), animals with APE induced by microspheres (500 mg, intravenously) treated 30 min later by intravenous physiological saline (Emb group) or intravenous adrenomedullin (50 ng/kg/min) during 30 min (Emb+Adm group). Plasma concentrations of cyclic adenosine (cAMP) and guanosine monophosphate (cGMP) were determined by enzyme immunoassay.

KEY FINDINGS

Variables did not change over time in sham animals. In both embolized groups, microsphere injection significantly (P<0.05) increased pulmonary vascular resistance index (PVRI) and mean pulmonary artery pressure (MPAP) from baseline by 181% and 111-142%, respectively (% change in mean values). Adrenomedullin significantly decreased PVRI (18%-25%) and significantly increased cardiac index (22%-25%) from values recorded 30 min after APE (E30), without modifying MPAP. Adrenomedullin decreased mean arterial pressure (18%-24%) and systemic vascular resistance index (32%-40%). Embolization significantly increased arterial-to-end tidal CO2 gradient, alveolar-to-arterial O2 gradient, and pulmonary shunt fraction from baseline, but these variables were unaffected by adrenomedullin. While adrenomedullin significantly increased plasma cAMP, cGMP levels were unaltered.

SIGNIFICANCE

Adrenomedullin induces systemic and pulmonary vasodilation, possibly via a cAMP mediated mechanism, without modifying the gas exchange impairment associated with APE. The pulmonary anti-hypertensive effect of adrenomedullin may be offset by increases in cardiac index.

[Estrogen reduced myocardial damage by regulating Gαs-cAMP pathway in isoprenaline injured rats]

The aim of the present study is to explore the mechanism of estrogen on regulating cardiac function disorder by adjusting the stimulating adenylate cyclase G α protein (Gαs)-cycle adenosine monophosphate (cAMP) signal pathway. Adult female rats were randomly divided into five groups: sham group, ovariectomized group (OVX), OVX and 17β-estradiol given group (OVX+E₂), OVX and isoprenaline injected group (OVX+ISO), OVX and 17β-estradiol, isoprenaline injected group (OVX+E₂+ISO). Rats were ovariectomized, and two weeks later, OVX+E₂group was injected with E₂, OVX+ISO group was injected with ISO, OVX+E₂+ISO group was injected with E₂and ISO. Another four weeks later, the hemodynamic parameters were monitored by carotid artery intubation: left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), maximal differentials of left ventricular developed pressure (+dp/dt(max)), and minimal differentials of left ventricular developed pressure (-dp/dt(max)). Brain natriuretic peptide (BNP) and cAMP concentration in plasma were determined; Gα(s) protein expression in myocardium was determined. The results showed that the hemodynamic parameters, the concentration of BNP and cAMP in plasma had no significant changes after ovariectomy compared with sham group. But after isoprenaline injection in ovariectomized rats, LVSP and +dp/dt(max) declined (P < 0.01), LVEDP and -dp/dt(max) elevated (P < 0.01); plasma BNP concentration increased (P < 0.01); plasma cAMP concentration decreased (P < 0.01), compared with OVX group. Further estrogen supplements improved the heart function treated by isoprenaline: LVSP and +dp/dt(max) elevated (P < 0.01), LVEDP and -dp/dtmax declined (P < 0.05, P < 0.01); the plasma BNP concentration decreased (P < 0.01); the plasma cAMP concentration increased (P < 0.01). Estrogen had no significant influence on Gαs protein expression. The results suggest that estrogen can alleviate myocardial injury and regulate cardiac function disorder by increasing cAMP level, finally improved the excessive suppression of myocardium.

The clinical correlation of regulatory T cells and cyclic adenosine monophosphate in enterovirus 71 infection

Background

Brainstem encephalitis (BE) and pulmonary edema (PE) are notable complications of enterovirus 71 (EV71) infection.

Objective

This study investigated the immunoregulatory characterizations of EV71 neurological complications by disease severity and milrinone treatment.

Study Design

Patients <18 years with virologically confirmed EV71 infections were enrolled and divided into 2 groups: the hand, foot, and mouth disease (HFMD) or BE group, and the autonomic nervous system (ANS) dysregulation or PE group. Cytokine and cyclic adenosine monophosphate (cAMP) levels, and the regulatory T cell (Tregs) profiles of the patients were determined.

Results

Patients with ANS dysregulation or PE exhibited significantly low frequency of CD4⁺CD25⁺Foxp3⁺ and CD4⁺Foxp3⁺ T cells compared with patients with HFMD or BE. The expression frequency of CD4⁻CD8⁻ was also significantly decreased in patients with ANS dysregulation or PE. Among patients with ANS dysregulation or PE, the expression frequency of CD4⁺Foxp3⁺ increased markedly after milrinone treatment, and was associated with reduction of plasma levels IL-6, IL-8 and IL-10. Plasma concentrations of cAMP were significantly decreased in patients with ANS dysregulation or PE compared with patients with HFMD or BE; however, cAMP levels increased after milrinone treatment.

Conclusions

These findings suggested decreased different regulatory T populations and cAMP expression correlate with increased EV71 disease severity. Improved outcome after milrinone treatment may associate with increased regulatory T populations, cAMP expression and modulation of cytokines levels.

[The ratio of hormones of system "hypophysis - thyroid" with level of dopamine and cyclic adenosine mono-phosphate of males in European north]

The study sampling consisted of 96 males from Arkhangelsk and 52 males from village of Nes. The examination was carried out to find out predominant regulative effect of dopamine on the system "hypophysis - thyroid" depending on territory of residence. In males of Zapolyarye, against the background of higher levels of T4, fT3 and TSH and cyclic adenosine mono-phosphate in blood occurs decreasing of levels of thyroglobulin and dopamine in comparison with males of circumpolar territories in case of registration of positive correlation between levels of dopamine and fT3. In males from circumpolar territories age-related decreasing of range of variations of level of dopamine and fT4 under increase of concentration of TSH was registered. At that, negative correlation between content of dopamine and T4 was registered. The age-related dynamics of alteration of level of cyclic adenosine monophosphate with tendency to increase in males of Zapolyarye at the age of 36-60 years in comparison with age group of 22-35 years.

[Role of catecholamine hormone in heroin addicts]

OBJECTIVE

To investigate the effects of catecholamine hormone on the blood and brain of heroin addicts.

METHODS

Rats were divided into three groups and treated with the glucose (control group), the heroin (im) (heroin group), and the combination of the intramuscular injection of reserpine and heroin (reserpine group). Changes in the levels of the dopamine (DA), cAMP, and cGMP were detected by the radioimmunoassay (RIA) method in the blood and brain tissue.

RESULTS

No significant withdrawal symptoms were observed in the reserpine group. Compared with the control and heroin groups, the blood cAMP levels were increased by 35.36% and 15.53% in the reserpine group, respectively; the cAMP levels in the midbrain ventral tegmental area (VTA), prefrontal cortex (PFC), and hippocampus (Hipp) were increased by 24.08% & 8.53%, 15.66% & 8.13%, and 21.95% & 8.40%, respectively. While compared to the control and heroin groups, the DA levels of the PFC, Hipp, striatum, and nucleus accumbens (NAc) were significantly reduced in the reserpine group, decreasing by 74.09% & 82.86%, 81.06% & 82.23%, 91.62% & 86.55% and 84.35% & 90.63%, respectively. The concentrations of cGMP of the brain tissues in the reserpine group were lower than those in the control group. In addition, the neural electrophysiological testing showed that the electroencephalogram (EEG), electrocardiogram (ECG), and muscle spindle discharge diagram of rats in both the reserpine and heroin groups were apparently changed.

CONCLUSION

Catecholamine hormone plays an important role in heroin addiction.

Acute response to oral calcium loading in pregnant and lactating women with a low calcium intake: a pilot study

This pilot study in women from The Gambia with low habitual calcium intakes showed differences in calciotropic hormones between pregnant, lactating and non-pregnant, non-lactating women similar to those in Western women. The response to oral calcium loading indicates a high degree of calcium conservation independent of reproductive status.

INTRODUCTION

In pregnancy and early lactation, parathyroid hormone (PTH) concentrations may be suppressed. Uncertainty exists about how calcium metabolism is regulated, particularly when calcium intake is low.

METHODS

We investigated fasting markers of calcium metabolism and the acute calcemic and calciuric responses after an oral calcium load in 30 pregnant, lactating or non-pregnant, non-lactating (NPNL) Gambian women with low habitual calcium intakes. Women received 1 g elemental calcium (CaCO3) at 0 min. Blood was collected at -30 and 180 min. Urine was collected from -60 to 0, 0-120 and 120-240 min. Samples were analysed (blood: ionized calcium (iCa); plasma (p): total calcium (tCa), phosphate (P), creatinine (Cr), PTH, 1,25-dihydroxyvitamin D (1,25(OH)2D), osteocalcin (OC), β C-terminal cross-linked telopeptide of type 1 collagen (βCTX), cyclic adenosine monophosphate (cAMP); urine (u): Ca, P, Cr, cAMP).

RESULTS

Pre-loading, groups did not differ significantly in iCa, pP, uCa/Cr and uP/Cr. pOC concentrations were significantly lower and NcAMP and p1,25(OH)2D higher in pregnant women; pPTH and pβCTX in lactating women were higher than in NPNL women. Post-loading, iCa, ptCa and uCa/Cr concentrations increased; pPTH, NcAMP, βCTX and uP/Cr decreased in all groups, but the magnitude of change did not differ significantly between groups.

CONCLUSION

Differences between pregnant, lactating and NPNL Gambian women in pPTH, NcAMP and p1,25(OH)2D and bone markers were similar to Western women. However, the response to calcium loading indicates that there may be no differences in renal and intestinal calcium economy associated with reproductive status, potentially due to a high degree of calcium conservation associated with low intakes.

[Study on the regulation role of semen persicae to cAMP-PKA signal pathway in the rats with cold and heat blood stasis syndrome]

OBJECTIVE

To study the regulation role of with neutral property to cAMP-PKA pathway in the rats with cold and heat blood stasis syndromes and it's mechanism.

METHODS

60 rats were randomly divided into normal control group, model control group, Semen Persicae group, radix salvia miltiorrhiza group, rhizoma chuanxiong group, 12 rats per group. The three herb groups were orally given relative herbs decoction, whose dosages were equal to 10 times the human clinical dose, normal and model control groups were orally given water, 2 times/day, 20 mL/kg, for 7 days. Experiments in rats with cold and heat blood stasis syndromes were carried on respectiverly. In heat blood stasis syndromes, except normal control group, the other groups were intraperitoneally injected 10% carrageenan, 5 mL/kg, 1 times/day, for 3 days;24 hours after the last injection, subcutaneously injected 20% dry yeast suspension, 10 mL/kg. In cold blood stasis syndromes, except normal control group, the other groups were put into fridge, temperature--(18 +/- 2) degrees C, 2 hours/ times, 2 times/day, for 7 days. Separately draw 5 ml abdominal aortic blood and taken abdominal aorta, 6 hours and 12 hours after finishing the model in the two syndromes. Tested the cAMP content by elisa, tested the PKA protein expression by Western blot.

RESULTS

Semen Persicae with neutral property, could decrease the content of cAMP in plasma (P < 0.01), inhibit the expression of protein PKA (P < 0.05) in rats with heat stagnation and blood stasis syndrome, increase the plasma content of cAMP (P < 0.01) and increase the expression of protein PKA (P < 0.01) in rats with cold stagnation and blood stasis syndrome. Semen Persicae had two-way adjustment action on CAMP-PKA signal pathway.

CONCLUSION

In different internal environment of heat stagnation and blood stasis syndrome, cold stagnation and blood stasis syndrome, Semen Persicae with neutral property has two-way adjustment to cAMP-PKA signaling channel, which may be one of the mechanism of it's two-way application.

The absence of mrp4 has no effect on the recruitment of neutrophils and eosinophils into the lung after LPS, cigarette smoke or allergen challenge

The multidrug resistance protein 4 (Mrp4) is an ATP-binding cassette transporter that is capable of exporting the second messenger cAMP from cells, a process that might regulate cAMP-mediated anti-inflammatory processes. However, using LPS- or cigarette smoke (CS)-inflammation models, we found that neutrophil numbers in the bronchoalveolar lavage fluid (BALF) were similar in Mrp4^−/− and Mrp4^+/+ mice treated with LPS or CS. Similarly, neutrophil numbers were not reduced in the BALF of LPS-challenged wt mice after treatment with 10 or 30 mg/kg of the Mrp1/4 inhibitor MK571. The absence of Mrp4 also had no impact on the influx of eosinophils or IL-4 and IL-5 levels in the BALF after OVA airway challenge in mice sensitized with OVA/alum. LPS-induced cytokine release in whole blood ex vivo was also not affected by the absence of Mrp4. These data clearly suggest that Mrp4 deficiency alone is not sufficient to reduce inflammatory processes in vivo. We hypothesized that in combination with PDE4 inhibitors, used at suboptimal concentrations, the anti-inflammatory effect would be more pronounced. However, LPS-induced neutrophil recruitment into the lung was no different between Mrp4^−/− and Mrp4^+/+ mice treated with 3 mg/kg Roflumilast. Finally, the single and combined administration of 10 and 30 mg/kg MK571 and the specific breast cancer resistance protein (BCRP) inhibitor KO143 showed no reduction of LPS-induced TNFα release into the BALF compared to vehicle treated control animals. Similarly, LPS-induced TNFα release in murine whole blood of Mrp4^+/+ or Mrp4^−/− mice was not reduced by KO143 (1, 10 µM). Thus, BCRP seems not to be able to compensate for the absence or inhibition of Mrp4 in the used models. Taken together, our data suggest that Mrp4 is not essential for the recruitment of neutrophils into the lung after LPS or CS exposure or of eosinophils after allergen exposure.

Increased platelet activation and thrombosis in transgenic mice expressing constitutively active P2Y12

BACKGROUND

In our previous in vitro study, we reported a constitutively active chimeric P2Y(12) (cP2Y(12)) and found that AR-C78511 is a potent inverse agonist at this receptor. The role of cP2Y(12) in platelet activation and thrombosis is not clear.

OBJECTIVES

To investigate the physiologic implications of cP2Y(12) for platelet activation and thrombus formation, and to evaluate the antiplatelet activity of AR-C78511 as an inverse agonist.

METHODS AND RESULTS

We generated transgenic mice conditionally and platelet-specifically expressing cP2Y(12). High-level expression of cP2Y(12) in platelets increased platelet reactivity, as shown by increased platelet aggregation in response to multiple platelet agonists. Moreover, transgenic mice showed a shortened bleeding time, and more rapid and stable thrombus formation in mesenteric artery injured with FeCl(3). The constitutive activity of cP2Y(12) in platelets was confirmed by decreased platelet cAMP levels and constitutive Akt phosphorylation in the absence of agonists. AR-C78511 reversed the cAMP decrease in transgenic mouse platelets, and exhibited a superior antiplatelet effect to that of AR-C69931MX in transgenic mice.

CONCLUSIONS

These findings further emphasize the importance of P2Y(12) in platelet activation, hemostasis, and thrombosis, as well as the prothrombotic role of the constitutive activity of P2Y(12). Our data also validate the in vivo inverse agonist activity of AR-C78511, and confirm its superior antiplatelet activity over neutral antagonists.

Dietary resveratrol prevents the development of food allergy in mice

Background

Resveratrol is a bioactive polyphenol enriched in red wine that exhibits many beneficial health effects via multiple mechanisms. However, it is unclear whether resveratrol is beneficial for the prevention of food allergy. This study investigated whether resveratrol inhibited the development of food allergy by using a mouse model of the disease.

Methodology/Principal Findings

Mice fed standard diet or standard diet plus resveratrol were sensitized by intragastric administration of ovalbumin (OVA) and mucosal adjuvant cholera toxin (CT). Several manifestations of food allergy were then compared between the mice. The effects of resveratrol on T cells or dendritic cells were also examined by using splenocytes from OVA-specific T cell-receptor (TCR) transgenic DO11.10 mice or mouse bone marrow-derived dendritic cells (BMDCs) in vitro. We found that mice fed resveratrol showed reduced OVA-specific serum IgE production, anaphylactic reaction, and OVA-induced IL-13 and IFN-ã production from the mesenteric lymph nodes (MLNs) and spleens in comparison to the control mice, following oral sensitization with OVA plus CT. In addition, resveratrol inhibited OVA plus CT-induced IL-4, IL-13, and IFN-ã production in splenocytes from DO11.10 mice associated with inhibition of GATA-3 and T-bet expression. Furthermore, resveratrol suppressed the OVA plus CT-induced CD25 expression and IL-2 production in DO11.10 mice-splenocytes in association with decreases in CD80 and CD86 expression levels. Finally, resveratrol suppressed CT-induced cAMP elevation in association with decreases in CD80 and CD86 expression levels in BMDCs.

Conclusions/Significance

Ingestion of resveratrol prevented the development of a food allergy model in mice. Given the in vitro findings, resveratrol might do so by inhibiting DC maturation and subsequent early T cell activation and differentiation via downregulation of CT-induced cAMP activation in mice. These results suggest that resveratrol may have potential for prophylaxis against food allergy.

Effect of trichlorfon on hepatic lipid accumulation in crucian carp Carassius auratus gibelio

This study evaluated the toxic effects of the organophosphate pesticide trichlorfon on hepatic lipid accumulation in crucian carp Carassius auratus gibelio. Seventy-five fish were divided into five groups (each group in triplicate), and then exposed to 0, 0.5, 1.0, 2.0, and 4.0 mg/L of trichlorfon and fed with commercial feed for 30 d. At the end of the experiment, plasma and hepatic lipid metabolic biochemical status were analyzed. Triglyceride contents were significantly (P < 0.05) increased in liver but decreased in plasma after 1.0, 2.0, and 4.0 mg/L trichlorfon treatments. Plasma insulin contents were markedly (P < 0.05) increased when trichlorfon concentrations were 0.5, 1.0, and 4.0 mg/L. There were no significant differences in hepatic hormone-sensitive lipase contents between the trichlorfon-treated fish and the controls. Hepatic cyclic adenosine 3', 5'-monophosphate, very-low-density lipoprotein, and apolipoprotein B100 contents were decreased in the fish when trichlorfon concentration was 2.0 mg/L. Furthermore, electron microscope observations showed rough endoplasmic reticulum dilatation and mitochondrial vacuolization in hepatocytes with trichlorfon exposure. On the basis of morphological and physiological evidence, trichlorfon influenced crucian carp hepatic pathways of lipid metabolism and hepatocellular ultrastructure, which resulted in lipid accumulation in the liver.

[Changes of adhesion molecules and adenosine in divers post 480 heliox saturation diving]

OBJECTIVE

To investigate the changes of adhesion molecules, cyclic adenosine monophosphate(cAMP) and cyclic guanosine monophosphate (cGMP) in divers post 480 heliox saturation diving.

METHODS

Four divers were compressed within 96 hours to depths of 480 m with heliox-oxygen and held at the designated depth for 49 hours, excursion to 493 m during their saturation stay, then decompressed within 302 hours to the surface. The blood samples were collected before compression and post decompression, the expression level of intercellular adhesion molecule-1(ICAM-1), E-selectin, P-selectin, cAMP, cGMP were detected with ELISA analysis box.

RESULTS

Compared with the levels of CAMs before compression, the levels of ICAM-1, E-selectin, P-selectin and cGMP in the serum were changed post decompression (P > 0.05). The levels of cAMP were significantly elevated post decompression (629.91 +/- 75.01) nmol/L vs (66.72 +/- 83.15) (P < 0.05).

CONCLUSION

The decompression schedule in this heliox saturation diving is safe, the decompression sickness pathology in this diving has not been induced. But the stress response of divers are enhanced by this great depth saturation diving.

Mechanism of FGF23 processing in fibrous dysplasia

Fibroblast growth factor-23 (FGF23) is a phosphate- and vitamin D-regulating hormone derived from osteoblasts/osteocytes that circulates in both active (intact, iFGF23) and inactive (C-terminal, cFGF23) forms. O-glycosylation by O-glycosyl transferase N-acetylgalactosaminyltransferase 3 (ppGalNAcT3) and differential cleavage by furin have been shown to be involved in regulating the ratio of active to inactive FGF23. Elevated iFGF23 levels are observed in a number of hypophosphatemic disorders, such as X-linked, autosomal recessive, and autosomal dominant hypophosphatemic rickets, whereas low iFGF23 levels are found in the hyperphosphatemic disorder familial tumoral calcinosis/hyperphosphatemic hyperostosis syndrome. Fibrous dysplasia of bone (FD) is associated with increased total FGF23 levels (cFGF23 + iFGF23); however, classic hypophosphatemic rickets is uncommon. Our results suggest that it can be explained by increased FGF23 cleavage leading to an increase in inactive cFGF23 relative to active iFGF23. Given the fact that FD is caused by activating mutations in the small G-protein G(s) α that results in increased cyclic adenosine monophosphate (cAMP) levels, we postulated that there may be altered FGF23 cleavage in FD and that the mechanism may involve alterations in cAMP levels and ppGalNacT3 and furin activities. Analysis of blood specimens from patients with FD confirmed that the elevated total FGF23 levels are the result of proportionally increased cFGF23 levels, consistent with less glycosylation and enhanced cleavage by furin. Analysis of primary cell lines of normal and mutation-harboring bone marrow stromal cells (BMSCs) from patients with FD demonstrated that BMSCs harboring the causative G(s) α mutation had higher cAMP levels, lower ppGalNAcT3, and higher furin activity. These data support the model wherein glycosylation by ppGalNAcT3 inhibits FGF23 cleavage by furin and suggest that FGF23 processing is a regulated process that controls overall FGF23 activity in FD patients.

A new apparatus and surgical technique for the dual perfusion of human tumor xenografts in situ in nude rats

We present a new perfusion system and surgical technique for simultaneous perfusion of 2 tissue-isolated human cancer xenografts in nude rats by using donor blood that preserves a continuous flow. Adult, athymic nude rats (Hsd:RH-Foxn1(rnu)) were implanted with HeLa human cervical or HT29 colon adenocarcinomas and grown as tissue-isolated xenografts. When tumors reached an estimated weight of 5 to 6 g, rats were prepared for perfusion with donor blood and arteriovenous measurements. The surgical procedure required approximately 20 min to complete for each tumor, and tumors were perfused for a period of 150 min. Results showed that tumor venous blood flow, glucose uptake, lactic acid release, O(2) uptake and CO(2) production, uptake of total fatty acid and linoleic acid and conversion to the mitogen 13-HODE, cAMP levels, and activation of several marker kinases were all well within the normal physiologic, metabolic, and signaling parameters characteristic of individually perfused xenografts. This new perfusion system and technique reduced procedure time by more than 50%. These findings demonstrate that 2 human tumors can be perfused simultaneously in situ or ex vivo by using either rodent or human blood and suggest that the system may also be adapted for use in the dual perfusion of other organs. Advantages of this dual perfusion technique include decreased anesthesia time, decreased surgical manipulation, and increased efficiency, thereby potentially reducing the numbers of laboratory animals required for scientific investigations.

Novel roles of cAMP/cGMP-dependent signaling in platelets

Endothelial prostacyclin and nitric oxide potently inhibit platelet functions. Prostacyclin and nitric oxide actions are mediated by platelet adenylyl and guanylyl cyclases, which synthesize cyclic AMP (cAMP) and cyclic GMP (cGMP), respectively. Cyclic nucleotides stimulate cAMP-dependent protein kinase (protein kinase A [PKA]I and PKAII) and cGMP-dependent protein kinase (protein kinase G [PKG]I) to phosphorylate a broad panel of substrate proteins. Substrate phosphorylation results in the inactivation of small G-proteins of the Ras and Rho families, inhibition of the release of Ca(2+) from intracellular stores, and modulation of actin cytoskeleton dynamics. Thus, PKA/PKG substrates translate prostacyclin and nitric oxide signals into a block of platelet adhesion, granule release, and aggregation. cAMP and cGMP are degraded by phosphodiesterases, which might restrict signaling to specific subcellular compartments. An emerging principle of cyclic nucleotide signaling in platelets is the high degree of interconnection between activating and cAMP/cGMP-dependent inhibitory signaling pathways at all levels, including cAMP/cGMP synthesis and breakdown, and PKA/PKG-mediated substrate phosphorylation. Furthermore, defects in cAMP/cGMP pathways might contribute to platelet hyperreactivity in cardiovascular disease. This article focuses on recent insights into the regulation of the cAMP/cGMP signaling network and on new targets of PKA and PKG in platelets.

Ent-16β,17-dihydroxy-kauran-19-oic acid, a kaurane diterpene acid from Siegesbeckia pubescens, presents antiplatelet and antithrombotic effects in rats

The antiplatelet and antithrombotic effects of ent-16β,17-dihydroxy-kauran-19-oic acid (DDKA) isolated from Siegesbeckia pubescens were investigated with different methods both in vitro and in vivo. We tested the antithrombotic activity of DDKA in arterio-venous shunt model. The effects of DDKA on adenosine diphosphate (ADP)-, Thrombin-, Arachidonic acid-induced rat platelets aggregation were tested in vitro. We also assessed its bleeding side effect by measuring coagulation parameters after intravenous administration for 5 days and investigated the potential mechanisms underlying such activities. In vivo, DDKA significantly reduced thrombus weight in the model of arterio-venous shunt. Meanwhile, DDKA increased plasma cAMP level determined by radioimmunoassay in the same model. Notably, DDKA prolonged PT and APTT in rats after intravenous administration DDKA for successive 5 days. In vitro, pretreatment with DDKA on washed rat platelets significantly inhibited various agonists stimulated platelet aggregation and caused an increase in cAMP level in platelets activated by ADP. These findings support our hypothesis that DDKA possesses antiplatelet and antithrombotic activities. The mechanisms underlying such activities may involve the anticoagulatory effect and cAMP induction.

Inhibitory effect of α-lipoic acid on platelet aggregation is mediated by PPARs

Peroxisome proliferator-activated receptors (PPARs) isoforms (α, β/δ, and γ are present in human platelets, and activation of PPARs inhibits platelet aggregation. α-Lipoic acid (ALA), occurring naturally in human food, has been reported to exhibit an antiplatelet activity. However, the mechanisms underlying ALA-mediated inhibition of platelet aggregation remain unknown. The aim of this study was to investigate whether the antiplatelet activity of ALA is mediated by PPARs. ALA itself significantly induced PPARα/γ activation in platelets and increased intracellular amounts of PPARα/γ by blocking PPARα/γ secretion from arachidonic acid (AA)-activated platelets. Moreover, ALA significantly inhibited AA-induced platelet aggregation, Ca(2+) mobilization, and cyclooxygenase-1 (COX-1) activity, but increased cyclic AMP production in rabbit washed platelets. Importantly, ALA also enhanced interaction of PPARα/γ with protein kinase Cα (PKCα) and COX-1 accompanied by an inhibition of PKCα activity in resting and AA-activated platelets. However, the above effects of ALA on platelets were markedly reversed by simultaneous addition of selective PPARα antagonist (GW6471) or PPARγ antagonist (GW9662). Taken together, the present study provides a novel mechanism by which ALA inhibition of platelet aggregation is mediated by PPARα/γ-dependent processes, which involve interaction with PKCα and COX-1, increase of cyclic AMP formation, and inhibition of intracellular Ca(2+) mobilization.

HIV-1 Tat-induced platelet activation and release of CD154 contribute to HIV-1-associated autoimmune thrombocytopenia

BACKGROUND

Enhanced platelet activation in human immunodeficiency virus (HIV)-1-infected patients has been reported and shown to strongly correlate with plasma viral load. Activated platelets are known to express and to release a variety of proteins that can modulate the immune system. Specifically, platelet-derived CD154 has been shown to be directly involved in the development of autoimmune thrombocytopenia (ITP). The mechanism by which HIV-1 infection leads to platelet activation and the effect of this activation on the development of HIV-1 ITP, however, is not fully understood.

OBJECTIVE

We have investigated the effect of HIV-1 Trans activating factor (Tat) on platelet activation.

RESULTS

We report that HIV-1 Tat directly interacts with platelets and induces platelet activation resulting in platelet micro-particle release. This activation by Tat requires the chemokine receptor CCR3 and β3-integrin expression on platelets, as well as calcium flux. Tat-induced activation of platelets releases platelet CD154, an immune modulator. Enhanced B-cell activity is found in mouse spleen B cells co-cultured with platelets treated with Tat in vitro. An early antibody response against adenovirus is found in Tat-injected mouse immunized with adenovirus, suggesting an enhanced immune response in vivo.

CONCLUSIONS

We have described a role of Tat-induced platelet activation in the modulation of the immune system, with implications for the development of HIV-1-associated thrombocytopenia.

Topical effects of roflumilast on 1-chloro-2,4-dinitrobenzene-induced atopic dermatitis-like skin lesions in NC/Nga mice

Phosphodiesterase-4 (PDE-4) inhibitors have a wide range of anti-inflammatory and immunomodulatory activities. Here we examined the effects of roflumilast, a well-known PDE-4 inhibitor, on 1-chloro-2,4-dinitrobenzene (DNCB)-induced atopic dermatitis-like lesions. Roflumilast inhibited DNCB-stimulated IL-1alpha secretion in HaCaT cells, and reduced ear thickness and lymph node weights in BALB/c mice sensitized with DNCB. Topical application of roflumilast to DNCB-induced atopic dermatitis-like skin lesions of NC/Nga mice ameliorated intensity scores and dorsal skin thickness, in parallel with reduced tissue IL-1beta levels and epidermal hyperplasia. On the other hand, no effect on IgE and IL-4 was observed upon roflumilast treatment. Taken together, roflumilast showed beneficial effects against DNCB-induced atopic dermatitis.

[Effect and mechanism of reserpine for changing salivary protein secretion in Pi-deficient rats]

OBJECTIVE

To study the effect of reserpine (RSP) for changing salivary protein secretion in Pi-deficient rats and to explore its possible mechanism.

METHODS

Twenty rats allocated in the RSP group were given subcutaneous injection of RSP [0.4 mg/(kg x d)] for 9 successive days, while the other 20 rats in the control group were injected with same volume of saline instead. On the 10th day, ten rats randomly selected from each group were subjected for extracting saliva to detect salivary amylase activity (sAA) before and after an acid stimulation; and drawing blood from the orbital vein to measure the contents of vasoactive intestinal peptide (VIP) and cyclic adenosine monophosphate (cAMP). Then they were sacrificed and their parotids were taken out for pathological examination with HE staining, as well as for VIP and cAMP measuring, and zymogen granules counting under a transmission electron microscope. The remainder animals were stopped injecting and normally fed to 40 days, then subjected to be detected as above-mentioned.

RESULTS

Food intake and body weight reduction were more significantly in the RSP group than in the control group. On the 10th day, the ratio of sAA before/after stimulation in the RSP group was 0.39 +/- 0.18, significantly lower than that in the control group (0.80 +/- 0.21, P < 0.01), but it was restored rapidly, reaching the normal range on the 25th day, on the 40th day, it became significantly different to the level on the 10th day (P < 0.05) and approached the level in the control group (P > 0.05). No significant pathological change of parotid was found in both groups; but the number of zymogen granules in the RSP group was remarkably more than that in the control group (41.4 +/- 4.9 vs 34.6 +/- 5.2, P < 0.01). Serum level of VIP in the RSP group was significantly less while that of cAMP was higher than that in the control group (22.5 +/- 13.1 mg/L vs 38.5 +/- 14.1 mg/L, and 125.8 +/- 15.5 micromol/L vs 105.3 +/- 16.7 micromol/L, both P < 0.05), but no inter-group difference was found in parotid tissue contents of both VIP and cAMP. All the indices detected became equivalent in the two groups on the 40th day.

CONCLUSION

The reduction of salivary protein in Pi-deficient rats induced by RSP may be related to the regulatory pathway of VIP and cAMP.

A new role for the A2b adenosine receptor in regulating platelet function

BACKGROUND

Activation of platelets is a critical component of atherothrombosis and plays a central role in the progression of unstable cardiovascular syndromes. Adenosine, acting through adenosine receptors, increases intracellular cAMP levels and inhibits platelet aggregation. The A2a adenosine receptor has already been recognized as a mediator of adenosine-dependent effects on platelet aggregation, and here we present a new role for the A2b adenosine receptor (A2bAR) in this process.

METHODS AND RESULTS

As compared with platelets from wild-type controls, platelets derived from A2bAR knockout mice have significantly greater ADP receptor activation-induced aggregation. Although mouse megakaryocytes and platelets express low levels of the A2bAR transcript, this gene is highly upregulated following injury and systemic inflammation in vivo. Under these conditions, A2bAR-mediated inhibition of platelet aggregation significantly increases. Our studies also identify a novel mechanism by which the A2bAR could regulate platelet aggregation; namely, ablation of the A2bAR leads to upregulated expression of the P2Y1 ADP receptor, whereas A2bAR-mediated or direct elevation of cAMP has the opposite effect. Thus, the A2bAR regulates platelet function beyond mediating the immediate effect of adenosine on aggregation.

CONCLUSIONS

Taken together, these investigations show for the first time that the platelet A2bAR is upregulated under stress in vivo, plays a significant role in regulating ADP receptor expression, and inhibits agonist-induced platelet aggregation.

[The role of prostaglandins in platelet aggregation in metabolic syndrome]

The role of metabolic products of arachidonic acid and thromboxans in metabolic syndrome was evaluated in 42 patients and 16 healthy subjects. The levels of arachidonic acid and thromboxane were shown to be elevated in patients with metabolic syndrome which accounted for enhanced platelet aggregation in response to ADP, adrenaline, and collagen. It is concluded that that decreased level of cyclic nucleotides (cAMP) and prostacyclin in combination with a rise in the content of Willebrand factor in patients with metabolic syndrome is a major contributor to the development of platelet activity.

Glucagon effects on plasma cyclic AMP and other reactants in normals and low insulin responders

The metabolic response to i.v. glucagon was evaluated in 11 normal individuals and 8 healthy low insulin responders. Elevations of plasma cyclic AMP and blood glucose were similar in both groups. Accordingly, no indications were seen of differing hepatic responsiveness to glucagon. In contrast, the groups differed in the course of plasma glycerol during the test.

The effect of glucagon on plasma cyclic AMP and glucose concentrations in patients with alcoholic cirrhosis

Glucagon was infused intravenously into four patients with alcoholic cirrhosis and five healthy subjects and serial measurements were made of plasma cyclic AMP and glucose concentrations. The results in the cirrhotic patients did not differ significantly from those in healthy subjects.

The effect of antilipolytic agents on cyclic AMP, free fatty acid and total catecholamine concentrations in plasma

Plasma concentrations of adenosine 3':5' cyclic monophosphate (cyclic AMP) and free fatty acids have been measured in 15 patients with acute myocardial infarction and in 6 dogs given infusions of isoprenaline. Plasma total catecholamines were also estimated in the patients. Inhibition of adipose tissue lipolysis with a nicotinic acid analogue did not decrease plasma cyclic AMP concentrations, either in the patients or when elevated in the dogs, thus suggesting that this tissue is not a major source of the nucleotide in plasma.

Nicotine stimulates pancreatic cancer xenografts by systemic increase in stress neurotransmitters and suppression of the inhibitory neurotransmitter gamma-aminobutyric acid

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer mortality in Western countries. We have shown previously that four representative human PDAC cell lines were regulated by beta-adrenoreceptors via cyclic adenosine 3',5'-monophosphate (cAMP)-dependent signaling. In the current study, we have tested the hypothesis that nicotine stimulates the growth of PDAC xenografts in nude mice by increasing the systemic levels of the stress neurotransmitters adrenaline and noradrenaline, which are the physiological agonists for beta-adrenoreceptors and that inhibition by gamma-aminobutyric acid (GABA) of the adenylyl cyclase-dependent pathway downstream of adrenoreceptors blocks this effect. The size of xenografts from PDAC cell line Panc-1 was determined 30 days after inoculation of the cancer cells. Stress neurotransmitters in serum as well as cAMP in the cellular fraction of blood and in tumor tissue were assessed by immunoassays. Levels of GABA, its synthesizing enzymes GAD65 and GAD67 and beta-adrenergic signaling proteins in the tumor tissue were determined by western blotting. Nicotine significantly increased the systemic levels of adrenaline, noradrenaline and cAMP while increasing xenograft size and protein levels of cAMP, cyclic AMP response element-binding protein and p-extracellular signal-regulated kinase 1/2 in the tumor tissue. Nicotine additionally reduced the protein levels of both GAD isozymes and GABA in tumor tissue. Treatment with GABA abolished these responses to nicotine and blocked the development of xenografts in mice not exposed to nicotine. These findings suggest that the development and progression of PDAC is subject to significant modulation by stimulatory stress neurotransmitters and inhibitory GABA and that treatment with GABA may be useful for marker-guided cancer intervention of PDAC.

Compound heterozygous mutations in the GNAS gene of a boy with morbid obesity, thyroid-stimulating hormone resistance, pseudohypoparathyroidism, and a prothrombotic state

CONTEXT

Pseudohypoparathyroidism type Ia and pseudopseudohypoparathyroidism are characterized by Albright's hereditary osteodystrophy (AHO), respectively, with and without hormone resistance. Both clinical conditions result from decreased expression or function of the alpha-subunit of the stimulatory G protein (Gsalpha) of adenylyl cyclase due to heterozygous inactivating mutations in GNAS. Homozygous GNAS defects have not been described.

OBJECTIVE

A genetic and functional GNAS study was undertaken in a boy with morbid obesity (body mass index Z-score of 5 at the age of 3 yr, with a body fat fraction of 40%, which is more than twice normal), TSH resistance, pseudohypoparathyroidism, and a prothrombotic state.

RESULTS

The boy was found to be a first case with a compound heterozygous GNAS defect: a de novo R231C mutation on the paternal allele and on the other allele a maternally inherited unique combination of three C to T nucleotide substitutions in exon 7 (I185I), intron 7 (IVS7 + 31), and exon 13 (N371N) leading to aberrant splicing of GNAS. Platelets of this boy displayed a pronounced Gsalpha hypofunction and were spontaneously hyperreactive resulting in a prothrombotic state due to extremely low cAMP levels.

CONCLUSION

This report expands the human GNAS genotype-phenotype spectrum to include compound heterozygosity and a prothrombotic state.

Rapid resensitization of purinergic receptor function in human platelets

BACKGROUND

Adenosine diphosphate (ADP) is a critical regulator of platelet activation, mediating its actions through two G protein-coupled receptors (GPCRs), the P2Y(1) and P2Y(12) purinergic receptors. Recently, we demonstrated that both receptors desensitize and internalize in human platelets by differential kinase-dependent mechanisms.

OBJECTIVES

To demonstrate whether responses to P2Y(1) and P2Y(12) purinergic receptors resensitize in human platelets and determine the role of receptor traffic in this process.

METHODS

These studies were undertaken either in human platelets or in cells stably expressing epitope-tagged P2Y(1) and P2Y(12) purinergic receptor constructs.

RESULTS

In this study we show for the first time that responses to both of these receptors can rapidly resensitize following agonist-dependent desensitization in human platelets. Further, we show that in human platelets or in 1321N1 cells stably expressing receptor constructs, the disruption of receptor internalization, dephosphorylation or subsequent receptor recycling is sufficient to block resensitization of purinergic receptor responses. We also show that, in platelets, internalization of both these receptors is dependent upon dynamin, and that this process is required for resensitization of responses.

CONCLUSIONS

This study is therefore the first to show that both P2Y(1) and P2Y(12) receptor activities are rapidly and reversibly modulated in human platelets, and it reveals that the underlying mechanism requires receptor trafficking as an essential part of this process.

Platelet and other tests followed sequentially for 14 days after operation

Nineteen patients were studied twice before and sequentially from 1 h to 14 days after operations lasting about 1 h. Eighteen tests were carried out, ideally on all the nine occasions blood collections were planned. Only significant changes are summarized. Immediately after the operation the plasma PF4 and beta TG were raised in parallel suggesting some platelet 'release' had occurred. At this time platelet aggregation to ADP and collagen had decreased by 57% to 64% and the plasma cyclic AMP had doubled. Next day these abnormalities had returned towards normal. By day 2 the fibrinogen and the heparin neutralizing activity were maximal; they returned towards normal by day 14. On day 14, when presumably all platelets present at operation had been removed the new platelets were 53% more numerous and 9.5% smaller; they contained 23% less PF4 and 42% less serotonin and 5-HT uptake was decreased, but the total amount of 5-HT and PF4 in the circulation probably remained constant. In summary these operations transitorily upset platelet function for a few hours and the platelets formed postoperatively were abnormal.

Effects of selective COX-2 inhibition on prostanoids and platelet physiology in young healthy volunteers

BACKGROUND

Selective inhibitors of cyclooxygenase-2 (COX-2) called coxibs, are effective anti-inflammatory and analgesic drugs. Recently, these drugs were associated with an increased risk for myocardial infarction and atherothrombotic events. The hypothesis of thromboxane-prostacyclin imbalance has been preferred to explain these unwanted effects.

METHODS

We studied the effects of 14 days intake of rofecoxib (25 mg q.d.), celecoxib (200 mg b.i.d.), naproxen (500 mg b.i.d.) and placebo in a randomized, blinded, placebo-controlled study in young healthy volunteers (median age 25-30 years, each group n = 10). We assessed prostanoid metabolite excretion (PGE-M, TXB(2), 6-keto-PGF(1alpha), 11-dehydro-TXB(2), 2,3-dinor-TXB(2), and dinor-6-keto-PGF(1alpha)), the expression of platelet activation markers (CD62P, PAC-1, fibrinogen), platelet-leukocyte formation, the endogenous thrombin potential, platelet cAMP content and plasma thrombomodulin level.

RESULTS

Naproxen suppressed biosynthesis of PGE-M, prostacyclin metabolites and thromboxane metabolites and thrombomodulin levels. In contrast, both coxibs had an inhibitory effect only on PGE-M, 6-keto-PGF(1alpha), and on dinor-6-keto-PGF(1alpha), whereas TXB(2), 2,3-dinor-TXB(2) and 11-dehydro-TXB(2) excretion were unaffected. None of the coxibs exerted significant effects on the expression of platelet activation markers, cAMP generation, platelet-leukocyte formation, or on thrombomodulin plasma levels. Interestingly, platelet TXB(2) release during aggregation was enhanced after coxib treatment following arachidonic acid or collagen stimulation.

CONCLUSION

In young healthy volunteers coxibs inhibit systemic PGE(2) and PGI(2) synthesis. Platelet function and expression of platelet aggregation markers are not affected; however, coxibs can stimulate TXB(2) release from activated platelets. Combined decrease in vasodilatory PGE(2) and PGI(2) together with increased TXA(2) in proaggregatory conditions may contribute to coxib side effects.

The greater in vivo antiplatelet effects of prasugrel as compared to clopidogrel reflect more efficient generation of its active metabolite with similar antiplatelet activity to that of clopidogrel's active metabolite

BACKGROUND AND METHODS

Prasugrel is a novel orally active thienopyridine prodrug with potent and long-lasting antiplatelet effects. Platelet inhibition reflects inhibition of P2Y(12) receptors by its active metabolite (AM). Previous studies have shown that the antiplatelet potency of prasugrel is at least 10 times higher than that of clopidogrel in rats and humans, but the mechanism of its higher potency has not yet been fully elucidated.

RESULTS

Oral administration of prasugrel to rats resulted in dose-related and time-related inhibition of ex vivo platelet aggregation, and its effect was about 10 times more potent than that of clopidogrel. The plasma concentration of prasugrel AM was higher than that of clopidogrel AM despite tenfold higher doses of clopidogrel, indicating more efficient in vivo production of prasugrel AM than of clopidogrel AM. In rat platelets, prasugrel AM inhibited in vitro platelet aggregation induced by adenosine 5'-diphosphate (ADP) (10 microm) with an IC(50) value of 1.8 microm. Clopidogrel AM similarly inhibited platelet aggregation with an IC(50) value of 2.4 microm. Similar results were also observed for ADP-induced (10 microm) decreases in prostaglandin E(1)-stimulated rat platelet cAMP levels. These results indicate that both AMs have similar in vitro antiplatelet activities.

CONCLUSIONS

The greater in vivo antiplatelet potency of prasugrel as compared to clopidogrel reflects more efficient in vivo generation of its AM, which demonstrates similar in vitro activity to clopidogrel AM.

Contributions of parathyroid hormone (PTH)/PTH-related peptide receptor signaling pathways to the anabolic effect of PTH on bone

PTH regulates osteoblastic function by activating PTH/PTHrP receptors (PTH1Rs), which trigger several signaling pathways in parallel, including cAMP/protein kinase A (PKA) and, via both phospholipase-C (PLC)-dependent and PLC-independent mechanisms, protein kinase C (PKC). These signaling functions have been mapped to distinct domains within PTH(1-34), but their roles in mediating the anabolic effect of intermittent PTH in vivo are unclear. We compared the anabolic effects in mice of hPTH(1-34) with those of two analogs having restricted patterns of PTH1R signaling. [G(1),R(19)]hPTH(1-28) lacks the 29-34 domain of hPTH(1-34) needed for PLC-independent PKC activation, incorporates a Gly(1) mutation that prevents PLC activation, and stimulates only cAMP/PKA signaling. [G(1),R(19)]hPTH(1-34) retains the 29-34 domain and activates both cAMP/PKA and PLC-independent PKC. Human PTH(1-34) (40 microg/kg), [G(1),R(19)]hPTH(1-34) (120 microg/kg), and [G(1),R(19)]hPTH(1-28) (800 microg/kg), at doses equipotent in elevating blood cAMP at 10 min and cAMP-dependent gene expression in bone at 6 h after s.c. injection, were administered to 10-week-old female C57BL/6J mice 5 days/week for 4 weeks. Acute blood cAMP responses, retested after 4 weeks, were not reduced by the preceding PTH treatment. The three PTH peptides induced equivalent increases in distal femoral bone mineral density (BMD), and, by microCT analysis, distal femoral and vertebral bone volume and trabecular thickness and mid-femoral cortical endosteal apposition. [G(1),R(19)]hPTH(1-34) and hPTH(1-34) increased distal femoral BMD more rapidly and augmented total-body BMD and bone volume of proximal tibial trabeculi to a greater extent than did [G(1),R(19)]hPTH(1-28). We conclude that cAMP/PKA signaling is the dominant mechanism for the anabolic actions of PTH in trabecular bone and that PLC-independent PKC signaling, attributable to the PTH(29-34) sequence, appears to accelerate the trabecular response and augment BMD at some skeletal sites. PTH1R PLC signaling pathway is not required for an anabolic effect of intermittent PTH(1-34) on bone.

Enhanced cAMP/PKA pathway by seabuckthorn fatty acids in aged rats

Seabuckthorn fatty acids were extracted by crushing and centrifuging from china seabuckthorn fruit. We detected cyclic nucleotides concentration in serum of different stages in aged rats (from 16 to 21 months), cyclic nucleotides concentration, PKA activity and PDE activity in hepatic tissue in aged rats by seabuckthorn fatty acids. Our data showed that the serum cAMP concentration decreased, accompany with the cGMP concentration increased and the imbalance of the cAMP/cGMP ratio in aged process. This kind of change equally in the hepatic tissue, the cAMP concentration decreased, PKA activity also decreased, but no change of the cAMP particularity PDE activity. And the SBFAs raised serum cAMP level in different stages, and raised the cAMP concentration and PKA activity of hepatic tissue, but did not effect the cAMP particularity PDE activity. Our study demonstrated that it is imbalance of the cAMP/cGMP ratio in aged process. SBFAs enhanced the cAMP/PKA pathway, regulated cAMP/cGMP ratio in aged rats.

Reduction of atherosclerotic nanoplaque formation and size by Ginkgo biloba (EGb 761) in cardiovascular high-risk patients

Coating a silica surface with the isolated lipoprotein receptor proteoheparan sulfate (HS-PG) from arterial endothelium and vascular matrices and adding both the atherogenic VLDL/IDL/LDL lipid fraction in its native composition and Ca(2+) ions, we could observe in vitro the earliest stages of atherosclerotic plaque development by ellipsometric techniques (patent EP 0 946 876). This so-called nanoplaque formation is represented by the ternary aggregational complex of the HS-PG receptor, lipoprotein particles and calcium ions. The model was validated in several clinical studies on statins in cardiovascular high-risk patients. In eight patients who had undergone an aortocoronary bypass operation, the reduction of atherosclerotic nanoplaque formation amounted to 11.9+/-2.5% (p<0.0078) and of nanoplaque size to 24.4+/-8.1% (p<0.0234), respectively, after a 2-month therapy with Ginkgo biloba extract (2x 120 mg daily, EGb 761). Additionally, superoxide dismutase (SOD) activity was upregulated by 15.7+/-7.0% (p<0.0391), the quotient oxLDL/LDL lowered by 17.0+/-5.5% (p<0.0234) and lipoprotein(a) concentration decreased by 23.4+/-7.9% (p<0.0234) in the patients' blood. The concentration of the vasodilating substances cAMP and cGMP was augmented by 37.5+/-9.1% (p<0.0078) and 27.7+/-8.3% (p<0.0156), respectively. A multiple regression analysis between the patients' VLDL/IDL/LDL lipoprotein fraction applied in the ellipsometry measurements as well as the further risk factors oxLDL/LDL and Lp(a) on the one hand and changes in nanoplaque formation on the other hand reveals a basis for a mechanistic explanation of nanoplaque reduction under ginkgo treatment. The atherosclerosis inhibiting effect is possibly due to an upregulation in the body's own radical scavenging enzymes and an attenuation of the risk factors oxLDL/LDL and Lp(a).

Possible role of exogenous cAMP to improve vascular endothelial dysfunction in hypertensive rats

The study has been designed to investigate the effect of 8-Br-cAMP, an activator of protein kinase A, in hypertension-induced vascular endothelial dysfunction. Rats were uninephroctomized and desoxycortisone acetate (DOCA) (40 mg/kg, s.c.) was administered to rats to produce hypertension (mean arterial blood pressure > 140 mmHg). Vascular endothelial dysfunction was assessed using isolated aortic ring preparation, electron microscopy of thoracic aorta and serum concentration of nitrite/nitrate. The expression of mRNA for p22phox and eNOS was assessed by using reverse transcriptase-polymerase chain reaction. Serum thiobarbituric acid reactive substances concentration and aortic superoxide anion concentration were estimated to assess oxidative stress. 8-Br-cAMP (5 mg/kg, i.p.) or atorvastatin (30 mg/kg, p.o.) prevented hypertension-induced attenuation of acetylcholine-induced endothelium-dependent relaxation, impairment of vascular endothelial lining, decrease in expression of mRNA for endothelial nitric oxide synthase (eNOS), serum nitrite/nitrate concentration and increase in expression of mRNA for p22phox, superoxide anion and serum TBARS. The ameliorative effect of 8-Br-cAMP was prevented by N-nitro-L-arginine methyl ester (25 mg/kg, i.p.) and glibenclamide (30 mg/kg, i.p.). It may be concluded that 8-Br-cAMP may stimulate expression and activity of eNOS and suppress expression of p22phox subunit of NADPH oxidase to reduce oxidative stress and subsequently improve vascular endothelial dysfunction.

Peri-operative decreased cAMP levels in long-term alcoholic patients

Long-term alcoholic patients have a five-fold higher risk of post-operative bleeding complications compared with nonalcoholic individuals. Serotonin increases and cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) decrease platelet aggregation. We examined the platelet-rich plasma levels of these substances and agonist-induced platelet aggregation in long-term alcoholic patients before and after surgery. Thirty-three consecutive patients (13 long-term alcoholics and 20 non-alcoholics) scheduled for tumour resections of the upper digestive tract were included in the study. The levels of cAMP were significantly decreased before and after surgery in long-term alcoholic patients, but there were no significant differences in cGMP and serotonin levels in alcoholic compared with non-alcoholic patients. In contrast to previous studies, no significantly altered aggregation responses in long-term alcoholics were found. A possible explanation is decreased inhibition through diminished cAMP levels; cGMP and serotonin do not seem to influence peri-operative haemostasis.